const fp = require('lodash/fp')
const { Maybe, Container } = require('./support')

// - 练习1：使用fp.add(x, y)和fp.map(f, x)创建一个能让functor里的值增加的函数ex1

// const fp = require('lodash/fp')
// const { Maybe, Container } = require('./support')
let maybe = Maybe.of([5, 6, 1])

let ex1 = (x) => {
  // todo
  return maybe.map(fp.map(a => fp.add(a, x)))
}
console.log(ex1(2))
// - 练习2：实现一个函数ex2，能够使用fp.first获取列表的第一个元素

// const fp = require('lodash/fp')
// const { Maybe, Container } = require('./support')
let xs = Container.of(['do', 'ray', 'me', 'fa', 'so', 'la', 'ti', 'do'])
let ex2 = () => {
  // todo
  return xs.map(fp.first)
}
console.log(ex2())

// - 练习3：实现一个函数ex3，使用safeProp和fp.first找到user的名字的首字母

// const fp = require('lodash/fp')
// const { Maybe, Container } = require('./support')
let safeProp = fp.curry(function(x, o) {
  return Maybe.of(o[x])
})
let user = { id: 2, name: 'Albert' }
let ex3 = () => {
  // todo
  let safe=safeProp('name',user)
  
  let names = safe.map(name=>name.split('')).map(fp.first)
  return names
}
console.log(ex3());
// - 练习4：使用Maybe重写ex4，不要有if语句

// const fp = require('lodash/fp')
// const { Maybe, Container } = require('./support')
// let ex4 = function(n) {
//   if (n) {
//     return parseInt(n)
//   }
// }

let ex4 = (n)=>{
  return Maybe.of(n).map(parseInt)
}

console.log(ex4(3.5));
